If my phone number is (212)555-1212 and Bob spoofs my number vias SMS to Alice, will Alice's reply be sent to Bob, me or both?
EDIT: The concern is that the spoof prompts Alice to disclose information that Bob should not have.
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Sent to you. Bob is simply spoofing your number not replacing/sharing it with you on the phone network. He can send on your behalf but not (as far as I know, or at least as easily) receive on your behalf.
EDIT: The only way this appears to be possible in such a way that Bob spoofs a number and can send and receive messages on the spoofed number is with much more unique software that generates "virtual SIM's" (as they called them) using fake, un-registered numbers.
The more common SMS spoofing in-which the spoof'er piggy-backs off a real number, they can only send not receive as all they are doing is manipulating the SMS headers.
A couple resources I found that cover this:
Sorry about lacking technical quality in these resources, this is not a very well formally documented "attack" since it appears every service that does SMS spoofing does it a little different than the last.